linux-ext4 - Re: riscv32 EXT4 splat, 6.8 regression?

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Date: Fri, 12 Apr 2024 18:59:19 +0200
From: Björn Töpel <bjorn@...nel.org>
To: Theodore Ts'o <tytso@....edu>
Cc: linux-fsdevel@...r.kernel.org, Alexander Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
 linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, Andreas
 Dilger <adilger.kernel@...ger.ca>, linux-ext4@...r.kernel.org, Conor
 Dooley <conor@...nel.org>, Anders Roxell <anders.roxell@...aro.org>
Subject: Re: riscv32 EXT4 splat, 6.8 regression?

"Theodore Ts'o" <tytso@....edu> writes:

> On Fri, Apr 12, 2024 at 04:57:08PM +0200, Björn Töpel wrote:
>> Hi!
>> 
>> I've been looking at an EXT4 splat on riscv32, that LKFT found [1]:
>
> I'm getting a "page not found" for [1]?

You are? It's working for me!

>> This was not present in 6.7. Bisection wasn't really helpful (to me at
>> least); I got it down to commit c604110e662a ("Merge tag 'vfs-6.8.misc'
>> of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs"), and when I
>> revert the commits in the vfs merge the splat went away, but I *really*
>> struggle to see how those are related...
>
> It sounds like you have a reliable repro; is it something that can be
> streamlined into a simple test program?  If so, is it something that
> can be reproduced on other architectures?  And could you make it
> available?

It's kind of streamlined: Linaro has this nice "tuxrun" tool, that can
be installed via pip, e.g.

  $ pipx install tuxrun

if you're on Debian.

Then you can get the splat by running:

  $ tuxrun  --runtime docker --device qemu-riscv32 --kernel https://storage.tuxsuite.com/public/linaro/lkft/builds/2esMBaAMQJpcmczj0aL94fp4QnP/Image.gz --parameters SKIPFILE=skipfile-lkft.yaml --parameters SHARD_NUMBER=10 --parameters SHARD_INDEX=1 --image docker.io/linaro/tuxrun-dispatcher:v0.66.1 --tests ltp-controllers

(--runtime knows "podman" as well)

You can pass your own kernel to --kernel, and the config for riscv32 can
be obtained here [2].

Build with "make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu-", and make
sure to have the riscv64 cross-compilation support (yes, same toolchain
for rv32!).

It's when the rootfs is mounted, and the kernel is looking an init.

I'll keep debugging -- it was more if anyone had seen it before. I'll
try to reproduce on some other 32b platform as well.

Thanks,
Björn

[2] https://storage.tuxsuite.com/public/linaro/lkft/builds/2esMBaAMQJpcmczj0aL94fp4QnP/config